Installing ISPConfig ssl installation certificate to a site?

hi all , im trying to install the SSL certificate that ISPConfig creates during the installation to mydomain.com (to a site), but i can only create new certificates, because i take ispconfig server.crt and server.csr and paste it in the text fields but it doesnt work and click on save... but nothing...

im doing this for security reasons i want to do a login page in my site to ISPConfig panel, but i dont want to send plain logins throught internet and i dont want to ask the users for two certificates, (one of the site, and another for ispconfig) so... how can i do that ?

falco thanks for ur answer, but i dont want to create a new certificate , the problem is that i want to create a login window in my website that connects directly with ispconfig, the problem is if i create a SSL certificate for my site, then when customer wants login have to accept first the certificate for my site and then the ispconfig ssl certificate. if i dont create a certificate for my site then the passwords are sent unencrypt and this is to dantgerous...

so the only solution that i found is to create my site with the same SSL certificate of ispconfig, by this way the customers only have to accept one ssl certificate and the passwords are sent secure.

I think you'd still have to accept the certificate twice, even if you use the same one in both sites, simply because you change the site (you leave your site and go to ISPConfig on port 81).
But I'm not quite sure...

You can try this: create an SSL certificate for the site in ISPConfig. Afterwards, you have all the certificates etc. in the ssl directory.
I would then copy the contents of the ISPConfig certificate files into the appropriate file in the ssl directory, like that: